MC_MoveAbsolute

Description

This function block performs a single-axis move to a specified endpoint position based on Axis, Position, Velocity, Acceleration, Deceleration, JerkIn physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time, and Direction parameters.

MC_MoveAbsolute

Figure 8-138: MC_MoveAbsolute

Time Diagram

The following figure shows two examples of the combination of two absolute move FunctionA function calculates a result according to the current value of its inputs. A function has no internal data and is not linked to declared instances. Blocks:

The left part of timing diagram illustrates the case if the Second Function BlockA function block groups an algorithm and a set of private data. It has inputs and outputs. is called after the First one. If First reaches the commanded position of 6000 (and the velocity is 0) then the output Done causes the Second FB to move to the position 10000
The right part of the timing diagram illustrates the case if the Second move Function Block starts the execution while the First FB is still executing. In this case the First motion is interrupted and aborted by the Test signal during the constant velocity of the First FB. The Second FB moves directly to the position 10000 although the position of 6000 is not yet reached

MC_MoveAbsolute: Timing Diagram

This function block starts a motion-related action and therefore stores data for calculations and error checking. Please see Calling Function Blocks Multiple Times in the Same Cycle if you are using a dual-core controller.

Arguments

Input

Execute

Description

Requests to queue the move

Data type

BOOL

Range

0, 1

Unit

N/A

Default

—

Axis

Description

Name of a declared instance of the AXIS_REF library function (for more details,About Axis Name and Number)

Data type

AXIS_REF

Range

[1,256]

Unit

N/A

Default

—

Position

Description

Endpoint position. If Rollover Position is nonzero, this value must be in the range

0 <= Position < Rollover Position

When not in Rollover mode, the input accepts a 64-bit floating point value.
When converted to feedback units, the range is [-2⁵¹,2⁵¹-1] feedback units.

Data type

LREAL

Range

[see Description]

Unit

User unit

Default

—

Velocity

Description

Velocity setpointSetpoint is the target value that an automatic control system, for example PID controller, will aim to reach

Data type

LREAL

Range

—

Unit

User unit/sec

Default

—

Acceleration

Description

Trapezoidal: Acceleration rate

S-curve: Maximum acceleration

If Acceleration is not valid, ErrorID is set to 21

Selection of Acceleration and Jerk Parameters for Function Blocks

Data type

LREAL

Range

—

Unit

User unit/sec²

Default

—

Deceleration

Description

Trapezoidal: Deceleration rate

S-curve: Unused

Data type

LREAL

Range

—

Unit

User unit/sec²

Default

—

Jerk

Description

Trapezoidal: 0

S-curve: Constant jerkIn physics, jerk is the rate of change of acceleration; more precisely, the derivative of acceleration with respect to time

If Jerk is not valid, ErrorID is set to 21

Selection of Acceleration and Jerk Parameters for Function Blocks

Data type

LREAL

Range

—

Unit

User unit/sec³

Default

—

Direction

Description

When Rollover Position is zero, a value of 0 must be specified.

When Rollover Position is nonzero, a value of 1, 2, 3, or 4 must be specified.

Value	Description
0	no direction specification
1	positive direction. The axis travels in the positive direction to the endpoint
2	shortest distance. The axis travels in the direction that provides the shortest distance to the endpoint
3	negative direction. The axis travels in the negative direction to the endpoint
4	last direction. The axis travels to the endpoint in the same direction as its previous move

If the Position input is the same as the axis's current position, then:

when Direction = 2 (shortest distance), the axis does not move and the Done output goes high indicating that the move has been completed.
when Direction = 1, 3, or 4, the axis travels in the specified direction, through one rollover cycle, and arrives back at the same position.

Data type

SINT

Range

[0,4]

Unit

N/A

Default

—

BufferMode

Description

0 = abort

1 = buffer

2 = blend to active

3 = blend to next

4 = blend to low velocity

5 = blend to high velocity

See table in Buffer Modes

Data type

SINT

Range

[0,5]

Unit

N/A

Default

—

Output

Done	Description	Indicates the move completed successfully. The Command Position has reached the endpoint.
	Data type	BOOL
Busy	Description	High from the moment the Execute input is one-shot to the time the move is ended
	Data type	BOOL
Active	Description	Indicates this move is the active move
	Data type	BOOL
CommandAborted	Description	Indicates the move was aborted
	Data type	BOOL
Error	Description	Indicates an invalid input was specified or the move was terminated due to an error
	Data type	BOOL
ErrorID	Description	Indicates the error if Error output is set to TRUE See table in PLCopen Function Block ErrorID Output
	Data type	INT

Example

Structured Text

            (* MC_MoveAbsolute S
T example *)
Inst_MC_MoveAbsolute( MovAbsReq, Axis1, 1234.567, 100.0, 100.0, 100.0, 0, 0, 0 );  //instance of MC_MoveAbsolute
MovAbsDone := Inst_MC_MoveAbsolute.Done;  //store done output into user defined variable
MovAbsBusy := Inst_MC_MoveAbsolute.Busy;
MovAbsActive := Inst_MC_MoveAbsolute.Active;
MovAbsAborted := Inst_MC_MoveAbsolute.CommandAborted;
MovAbsError := Inst_MC_MoveAbsolute.Error;
MovAbsErrID := Inst_MC_MoveAbsolute.ErrorID;

See also how this function is used in the Hole punch project here

Ladder Diagram

MC_MoveAbsolute: LD example

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